Transponders are used for instance in RFID systems. In this description the term transponder is used to describe a device which transmits a signal in response to a received signal. Transponders may operate in one frequency only or they may use multiple frequencies. For example, U.S. Pat. No. 7,091,860 B2 discloses a RFID transponder capable of utilising multiple operating frequencies. An ultra-high frequency (UHF) may be used for data transmission, and another frequency, for instance a high frequency (HF), may be used for field penetration. UHF is the international telecommunication union (ITU) designation for radio frequencies in the range between 300 MHz and 3 GHz, also known as the decimeter band as the wavelengths range from one to ten decimeters. HF is the ITU designation for radio frequencies between 3 and 30 MHz. It is also known as the decameter band or decameter wave as its wavelength range from one to ten decameters (ten to one hundred meters). Different communication protocols are typically applied for data to be sent and/or received in different frequencies. The multi-frequency RFID transponder according to U.S. Pat. No. 7,091,860 B2 may use one common memory for multiple operating frequencies. This solution usually allows minimising the chip area. This approach is also normally used for single protocol RFID tags, which thus contain only one instance of memory.
In the case of multi-frequency transponders, such as dual-frequency transponders, memory requirements are different for each communication protocol. For example, data sent and/or received by using a first communication protocol may need a larger memory space compared to the memory used by a second communication protocol. Also, performance, power consumption and timing requirements for the memories typically vary depending on the communication protocol. Thus, it becomes clear that having only one shared memory in multi-frequency transponders is not an optimal solution. If, on the other hand, two memories are used in a dual-frequency transponder for example, then currently it is not known how to access both memories by using only one communication protocol.